EGPA, also known as allergic granulomatosis angiitis, is a systemic vasculitis. EGPA is marked by three distinct symptoms: asthma; eosinophilia, evidenced by an excessive number of eosinophils in the blood and tissues; and vasculitis involving the skin, lungs, nerves, kidneys, and other organs. Nerve involvement may also occur in EGPA, causing pain, tingling, numbness, and muscle wasting in the hands and feet. Because EGPA patients may not show any visible signs of active disease, current methods of monitoring disease progression usually represent a period of extended inflammation and disease activity. Thus, patients may go untreated during a period of undetectable disease when damage might be preventable. This study will use novel scientific methods to identify new biomarkers that can be used to monitor disease activity in EGPA patients. These biomarkers may be used to help direct clinical care for EGPA patients and assist in future drug development.